In a process of manufacturing a semiconductor substrate (hereinafter, referred to simply as a “substrate”), conventionally, various processes are performed on a substrate having an insulating film such as an oxide film or the like thereon by using a substrate processing apparatus. By supplying a processing liquid onto a substrate having a surface on which a resist pattern is formed, for example, a process such as etching or the like is performed on the surface of the substrate. Further, after etching or the like is finished, a process of removing the resist from the substrate is also performed.
In a substrate processing apparatus disclosed in Japanese Patent Application Laid-Open No. 2009-200365, before the process using a processing liquid such as an SPM (sulfuric acid/hydrogen peroxide mixture) liquid or the like is performed, a liquid having electrical conductivity lower than the processing liquid is supplied to a processing area on a substrate and then the processing liquid is discharged to the processing area with the liquid existing therein. It is thereby possible, in the substrate processing apparatus, to prevent any local damage of the substrate due to the contact made between the substrate and the processing liquid. The local damage of the substrate refers to destruction of a field oxide film or a gate oxide film in the processing area, and the destruction is caused by bringing the processing area on the substrate into contact with the processing liquid which is electrically charged by the frictional electrification phenomenon between the processing liquid and a processing liquid nozzle.
A substrate to be processed by a substrate processing apparatus is subjected to a drying process such as dry etching, plasma CVD (Chemical Vapor Deposition), or the like, before being loaded into the substrate processing apparatus. In such a drying process, since electric charges are generated in a device, the substrate which is electrically charged is loaded into the substrate processing apparatus. Then, in the substrate processing apparatus, when a processing liquid having low electrical resistivity, such as an SPM liquid, is supplied onto the substrate, the electric charges in the device rapidly move from the device to the processing liquid (in other words, the electric charges are discharged into the processing liquid) and damage may be caused in the device by heat generation due to the movement of the electric charges. Then, it is thought to be effective to remove static electricity from the substrate by using an ionizer before supplying the processing liquid onto the substrate, but when the amount of electrostatic charges on the substrate is too large, it is hard to efficiently remove static electricity from the substrate.
On the other hand, in the substrate processing apparatus disclosed in Japanese Patent Application Laid-Open No. 2009-200365, if water is contained in the liquid to be supplied onto the substrate before the process using the processing liquid is performed, for example, in the process using the processing liquid, damage may be caused to the substrate by heat of reaction between sulfuric acid in the SPM liquid serving as the processing liquid and water. Further, if water-diluted processing liquid is used, the processing liquid, when supplied onto the substrate, may deteriorate the quality of the processing of the substrate. When the water-diluted processing liquid is partial mixture of the processing liquid and water, the liquid leads to ununiformity in the concentration of the processing liquid, which may deteriorate uniformity of the processing over the entire substrate.